1. Technical Field
The present invention relates to a flat panel display and, more particularly, to an organic electroluminescence (EL) display apparatus including a gate insulating layer having an opening defining pixels, and a method of fabricating the organic EL display apparatus.
2. Related Art
Flexible organic electroluminescence (EL) display apparatuses generally used include a flexible substrate such as a plastic substrate. The plastic substrate is not very heat-resistant, and thus, the flexible organic EL display apparatuses should be fabricated at a low temperature. Organic thin film transistors (OTFTs) which can operate at a low temperature can be used as switching devices in the flexible organic EL display apparatuses. The OTFTs have been actively researched as possible driving devices in next generation display apparatuses. Instead of a silicon layer, OTFTs use an organic layer as a semiconductor layer instead of using a silicon layer. The OTFTs can be classified into low polymer OTFTs such as oligothiophene and pentacene, and high polymer OTFTs such as polythiophene, according to organic material.
Organic EL display apparatuses can be classified as back emission type apparatuses, front emission type apparatuses, and dual emission type apparatuses according to the light emission path from organic layers. In the back emission type organic EL display apparatuses, the light emitted from an organic light emitting layer is radiated toward the substrate. In the front emission type organic EL display apparatuses, the light emitted from the organic light emitting layer is radiated in the opposite direction away from the substrate. In addition, in the dual emission type organic EL display apparatuses, the light emitted from the organic light emitting layer is radiated both toward and away from the substrate and in an opposite direction relative to the substrate.
The organic EL display apparatus, including the OTFT according to the conventional art, includes: a thin film transistor (TFT) including source and drain electrodes, a semiconductor layer, and a gate on a substrate; a protective layer on the TFT; and an organic light emitting device including a lower electrode, an organic layer, and an upper electrode on the protective layer. A gate insulating layer is formed between the source and drain electrodes and the gate. The lower electrode is connected to one of the source and drain electrodes of the TFT through a via hole formed in the protective layer. A pixel separation layer includes an opening exposing a portion of the lower electrode. The organic layer is formed on the exposed lower electrode in the opening, and then the upper electrode is formed on the organic layer.
A method of fabricating an organic EL display apparatus having the above structure includes: forming the TFT including the source and drain electrodes, the semiconductor layer, and the gate; forming the protective layer; forming the via hole using a mask; forming the lower electrode connected to the TFT through the via hole on the protective layer; forming the opening exposing the lower electrode; and forming the organic layer and the upper electrode. These above processes for fabricating the organic EL display apparatus are very complex.